Blood separation device comprising a filter and a capillary flow pathway exiting the filter

Abstract

A method for separating plasma from red blood cells and a device utilizing the method in which a low-pressure filter is interposed in a pathway between an inlet port and a reaction area. The sole driving force for the movement of plasma from the filter to the reaction area is capillary force provided by a tubular capillary. The filter is selected from glass microfiber filters of specified characteristics, which can operate in the absence of agglutinins, and filters capable of separating agglutinated red cells from plasma, which require the use of an agglutinin.

What is claimed is: 
     
       1. In a clinical diagnostic device comprising a housing having a fluid inlet port, a vented reaction area, and a capillary pathway connecting said inlet port and said reaction area and in which the driving force for the movement of liquid through said capillary pathway arises from capillary pressure, an improvement which comprises: a low-pressure filter interposed in said pathway, wherein said filter is selected from the group consisting of binderless glass microfiber filters having a particle size retention in the range from about 1 μm to about 3 μm, a flow path of from about 0.5 to about 0.5 mm, and a density in the range from about 0.10 to 0.30 g/cm 3  and comprises glass fibers having diameters essentially all in the range of from 0.10 to 4.0 μm with at least 60% of the fibers having diameters in the range of from 0.10 to 1.23 μm, wherein said device contains no agglutinin for red blood cells, whereby whole blood applied to said inlet port is separated into plasma and red blood cells by said low-pressure filter.   
     
     
       2. The device of claim 1, wherein said filter consists essentially of borosilicate glass fibers. 
     
     
       3. The device of claim 2, wherein said filter has a thickness of 0.50 to 0.80 nm, a particle size retention of from about 2.3 to 3.0 μm, and comprises glass fibers having diameters distributed over said range of from 0.10 to 1.23 μm so that 3 or 4 equal divisions of said range each contains a number of fibers varying by no more than 10 number percent.